Scientists have found a way to use thin slices of graphene to convert solar energy to direct current electricity. The discovery could lead to a whole array of new applications, including a whole new method of creating a sustainable energy source to power buildings of the future.
Graphene is a material made up of a single layer of carbon atoms arranged like a honeycomb. Discovered in 2004 by Professors Andre Geim and Kostya Novoselov, graphene is extracted from graphite, like that found in lead pencils. It is the strongest, thinnest, most conductive material known to science and has led to a wide variety of applications, from medical to smart phones to computer chips. Geim and Novoselov won the 2010 Nobel Prize in physics for their discovery.
Now, scientists from the University of Manchester and the University of Singapore have created ultra-thin graphene surfaces capable of absorbing sunlight and generating electricity as well or better than existing solar panels. These devices could one day be used to develop a kind of coating on the outside of buildings that would produce enough electricity to power all the appliances inside. They also would be capable of performing other functions, such as changing color, brightness. and temperature depending on environmental conditions.
Graphene’s remarkable properties come from its two-dimensional structure. While carbon can form three-dimensional lattices when it bonds with four other carbon atoms to form diamond, it can also form two-dimensional layers when it bonds to three other carbon atoms, creating graphene. The graphene layers are arranged in a hexagonal configuration.
When scientists combined graphene with single layers of positively charged transition metal dichalcogenides (TMDC) , they were able to create a very efficient and sensitive solar converter. Professor Novoselov expressed excitement about “the new physics and new opportunities, which are brought to us by heterostructures based on 2D atoic crystals. ” He added that these photoactive heterostructures expand the possibilities and pave the way for new types of experiments. He anticipated that as scientists create more and more complex heterostructures, the functionalities of these devices will become multifunctional.
University of Manchester researcher and lead author Dr Liam Britnell added: “It was impressive how quickly we passed from the idea of such photosensitive heterostructures to the working device. It worked practically from the very beginning and even the most unoptimised structures showed very respectable characteristics”
Professor Antonio Castro Neto, Director of the Graphene Research Centre at the National University of Singapore added: “We were able to identify the ideal combination of materials: very photosensitive TMDC and optically transparent and conductive graphene, which collectively create a very efficient photovoltaic device.
“We are sure that as we research more into the area of 2D atomic crystals we will be able to identify more of such complimentary materials and create more complex heterostructures with multiple functionalities. This is really an open field and we will explore it.”
Dr Cinzia Casiraghi, from The University of Manchester, added: “Photosensitive heterostructures would open a way for other heterostructures with new functionalities. Also, in future we plan for cheaper and more efficient heterostructure for photovoltaic applications.”
Images and more information is available from www.graphene.manchester.ac.uk
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